Stock Enhancement in Salmon & Maintenance of Historic Runs

W.E. Ricker has recently shown that the failure of present day salmon fisheries to maintain historically high yields may be due in part to the fact that different stocks, which are subjected to the same fishing pressure, have different biological productivities, and the equilibrium maximum sustained yield may cause smaller less productive stocks to reach very low levels or even go extinct. This author explores the problem in two ways: he first analytically examines the relationship between two stocks subjected to the same fishery, and then tests these conclusions against a much more complex numerical simulation model of a salmon fishery.